Recently, according to the demand for a lightweight automobile, in order to develop a light weight interior material, many researches to give a heat-resistance in an acrylonitrile-butadiene-styrene (ABS) resin have been developed, wherein the ABS resin has a superior impact resistance, chemical resistance, and processability, etc.
As a method for giving a heat-resistance in the ABS (acrylonitrile-butadiene-styrene) resin, a method for preparing a heat-resistant ABS by mixing a copolymer having a superior heat-resistance with a graft ABS polymer has been proposed. U.S. Pat. Nos. 3,010,936 and 4,659,790 disclose a method for preparing a heat-resistant ABS resin in which a partition or total amount of styrene used in the preparation of a heat-resistant copolymer is substituted with α-methyl styrene having a good heat-resistance. Japanese Patent Laid-open publication Nos. sho 58-206657, sho 63-162708, sho 63-235350, and U.S. Pat. No. 4,757,109 disclose a method for preparing a heat-resistant ABS resin including a maleimide compound, and a method of mixing a polycarbonate resin with the ABS, and a method of charging an inorganic material in the ABS, etc.
These heat-resistant ABS resins are generally produced as a pellet form, so that a processing step such as injection molding or extruding molding is in demand for the production of final products.
In case of preserving or transporting a heat-resistant ABS resin or a processing molded article at low temperature, especially under 0° C., an undesirable color tone change and common whitening may be occurred.
If a phenomenon known as “cold stress whitening” is happened, the original color of the molded articles is disappeared and it is especially harmful to a colored molded product.
In order to apply in a heat-resistant ABS resin or a processing molded article, the reduction degree of a cold stress whitening phenomenon should be excellent.
Therefore, the requirement of the heat-resistant ABS resin having superiority in reduction of a cold stress whitening has been increased, and as a method for preparing this thermoplastic resin, various methods for adding polyorganosiloxane of 10 to 200 ppm to thermoplastic polymer (Korean Patent Laid-open Publication No. 2002-0047285) have been developed.
Also, a heat-resistant ABS resin has many processing steps after injection molding and post-processability is important. Especially, a rear lamp housing of automobile is manufactured by injecting polymethylmethacrylate resin (PMMA), painting with thinner for even injected surface and beautiful appearance, depositing aluminum, and connecting PMMA sheets each other in constant temperature and pressure, and in painting process during the manufacturing process, if the spread property of paint is reduced, a thinner must be additionally applied, the thinner may cause the badness and waste of a painting process and the badness of a deposit appearance in an aluminum depositing process. Also, since a melting strand in hot-tool welding process is occurred, the hot-tool weldability is reduced and appearance badness is resulted due to unevenly adhesion. Therefore, a polymethylmethacrylate (PMMA) used as a rear lamp housing of automobile must be excellent in hot-tool weldability, pigmentation and paint spread property.
Also, as the level of feeling quality of users has been recently increased, the demand of a low gloss resin to perform more elegant atmosphere is increased. In addition, as environment problem comes to the front, a low gloss resin is in progress toward the direct use, abbreviating a low gloss painting or a process covering with pad.
The major principle applied to prepare this low gloss resin is that the smoothness of resin surface is controlled to be enlarged more than a visible light range, whereby the incident light is scattered, therefore, a low gloss effect is shown. The more specific methods are explained in the following three examples.
Firstly, as a method for improving an acrylonitrile-butadiene-styrene resin, the rubber particles having a large diameter of more than 2 μm, obtained through a bulk-polymerization, is used. But, the resin prepared through this method is that a low-glossy effect is insignificant, and impact strength and heat-resistance are poor.
Secondly, there is a method of introducing a low gloss filler having the particle size of more than 5 μm into a resin. The resin prepared by this method shows excellent formability, but is insufficient in low-gloss property, and especially, the deterioration of impact strength is serious.
Thirdly, there is a method for preparing a resin by using a graft-polymerization of a monomer such as ethylene-unsaturated carboxylic acid as modifier and an acrylonitrile-butadiene-styrene polymer prepared with emulsion polymerization.
The resin prepared through these methods shows an excellent low-gloss(y) property and is good in impact strength and all sorts of physical properties, therefore is widely used to give a low gloss effect onto the resin.
But, for applying it in a super heat-resistant thermoplastic resin, the heat-resistance thereof is poor. And in case of applying it in a weatherability resin such as an acrylonitrile-styrene-acrylate resin, the amount used of which is recently increased, weatherability is lowered.